A word used instead of saying:"fooled you!" after a prank. It first appeared in the series of "The Big Bang Theory" and is used by the character named Sheldon. It comes from the word "zing" which means to fool or rediculous someone. and just for a cool slang, the added the "ba" to it. And later the series added the "a" to it, and then it became "Bazinga".

So this is a conversation between all the characters where Sheldon fools everybody with his classic joke and then say:"Bazinga!" instead of fooled you!" or "Gotcha!":
Howard and Rajesh: "We're going to the goth club!"
Sheldon:"I've always wanted to go to a goth club!...... Bazinga!"

"A seven-stringed harp", as referenced by Will Cuppy in the first chapter about the Pharaoh Cheops or Khufu, in his book "The Decline and Fall of Practically Everybody." Dorset Press, New York, 1950. Cuppy was most certainly kidding, since the book was a satire, but I felt it was important to know that the fabrication of the term preceded "The Big Bang Theory" by about 60 years.

from the text:

"Personally, I would call the royal harem one of Khufu's main interests in life and one of his claims to our attention. Although we lack statistics, it must have been one of the largest in the ancient world, completely equipped with the very best concubines obtainable in Africa, all skilled in dancing, singing and playing on the bazinga, or seven-stringed harp."